sound.c

   1 /* gameplaySP
   2  *
   3  * Copyright (C) 2006 Exophase <exophase@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation; either version 2 of
   8  * the License, or (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  18  */
  19
  20
  21 #include "common.h"
  22 #include <SDL.h>
  23 u32 global_enable_audio = 1;
  24
  25 direct_sound_struct direct_sound_channel[2];
  26 gbc_sound_struct gbc_sound_channel[4];
  27
  28 u32 sound_frequency = 44100;
  29
  30 SDL_mutex *sound_mutex;
  31 static SDL_cond *sound_cv;
  32
  33 #ifdef PSP_BUILD
  34 u32 audio_buffer_size_number = 1;
  35 #else
  36 u32 audio_buffer_size_number = 8;
  37 #endif
  38
  39 u32 sound_on;
  40 static u32 audio_buffer_size;
  41 static s16 sound_buffer[BUFFER_SIZE];
  42 static u32 sound_buffer_base;
  43
  44 static u32 sound_last_cpu_ticks;
  45 static fixed16_16 gbc_sound_tick_step;
  46
  47 static u32 sound_exit_flag;
  48
  49 // Queue 1, 2, or 4 samples to the top of the DS FIFO, wrap around circularly
  50
  51 #define sound_timer_queue(size, value)                                        \
  52   *((s##size *)(ds->fifo + ds->fifo_top)) = value;                            \
  53   ds->fifo_top = (ds->fifo_top + 1) % 32;                                     \
  54
  55 void sound_timer_queue8(u32 channel, u8 value)
  56 {
  57   direct_sound_struct *ds = direct_sound_channel + channel;
  58   sound_timer_queue(8, value);
  59 }
  60
  61 void sound_timer_queue16(u32 channel, u16 value)
  62 {
  63   direct_sound_struct *ds = direct_sound_channel + channel;
  64   sound_timer_queue(8, value & 0xFF);
  65   sound_timer_queue(8, value >> 8);
  66 }
  67
  68 void sound_timer_queue32(u32 channel, u32 value)
  69 {
  70   direct_sound_struct *ds = direct_sound_channel + channel;
  71
  72   sound_timer_queue(8, value & 0xFF);
  73   sound_timer_queue(8, (value >> 8) & 0xFF);
  74   sound_timer_queue(8, (value >> 16) & 0xFF);
  75   sound_timer_queue(8, value >> 24);
  76 }
  77
  78 // Unqueue 1 sample from the base of the DS FIFO and place it on the audio
  79 // buffer for as many samples as necessary. If the DS FIFO is 16 bytes or
  80 // smaller and if DMA is enabled for the sound channel initiate a DMA transfer
  81 // to the DS FIFO.
  82
  83 #define render_sample_null()                                                  \
  84
  85 #define render_sample_left()                                                  \
  86   sound_buffer[buffer_index] += current_sample +                              \
  87    fp16_16_to_u32((next_sample - current_sample) * (fifo_fractional >> 8))    \
  88
  89 #define render_sample_right()                                                 \
  90   sound_buffer[buffer_index + 1] += current_sample +                          \
  91    fp16_16_to_u32((next_sample - current_sample) * (fifo_fractional >> 8))    \
  92
  93 #define render_sample_both()                                                  \
  94   dest_sample = current_sample +                                              \
  95    fp16_16_to_u32((next_sample - current_sample) * (fifo_fractional >> 8));   \
  96   sound_buffer[buffer_index] += dest_sample;                                  \
  97   sound_buffer[buffer_index + 1] += dest_sample                               \
  98
  99 #define render_samples(type)                                                  \
 100   while(fifo_fractional <= 0xFFFFFF)                                          \
 101   {                                                                           \
 102     render_sample_##type();                                                   \
 103     fifo_fractional += frequency_step;                                        \
 104     buffer_index = (buffer_index + 2) % BUFFER_SIZE;                          \
 105   }                                                                           \
 106
 107 void sound_timer(fixed8_24 frequency_step, u32 channel)
 108 {
 109   direct_sound_struct *ds = direct_sound_channel + channel;
 110
 111   fixed8_24 fifo_fractional = ds->fifo_fractional;
 112   u32 buffer_index = ds->buffer_index;
 113   s16 current_sample, next_sample, dest_sample;
 114
 115   current_sample = ds->fifo[ds->fifo_base] << 4;
 116   ds->fifo_base = (ds->fifo_base + 1) % 32;
 117   next_sample = ds->fifo[ds->fifo_base] << 4;
 118
 119   if(sound_on == 1)
 120   {
 121     if(ds->volume == DIRECT_SOUND_VOLUME_50)
 122     {
 123       current_sample >>= 1;
 124       next_sample >>= 1;
 125     }
 126
 127     switch(ds->status)
 128     {
 129       case DIRECT_SOUND_INACTIVE:
 130         render_samples(null);
 131         break;
 132
 133       case DIRECT_SOUND_RIGHT:
 134         render_samples(right);
 135         break;
 136
 137       case DIRECT_SOUND_LEFT:
 138         render_samples(left);
 139         break;
 140
 141       case DIRECT_SOUND_LEFTRIGHT:
 142         render_samples(both);
 143         break;
 144     }
 145   }
 146   else
 147   {
 148     render_samples(null);
 149   }
 150
 151   ds->buffer_index = buffer_index;
 152   ds->fifo_fractional = fp8_24_fractional_part(fifo_fractional);
 153
 154   if(((ds->fifo_top - ds->fifo_base) % 32) <= 16)
 155   {
 156     if(dma[1].direct_sound_channel == channel)
 157       dma_transfer(dma + 1);
 158
 159     if(dma[2].direct_sound_channel == channel)
 160       dma_transfer(dma + 2);
 161   }
 162 }
 163
 164 void sound_reset_fifo(u32 channel)
 165 {
 166   direct_sound_struct *ds = direct_sound_channel;
 167
 168   memset(ds->fifo, 0, 32);
 169 }
 170
 171 // Initial pattern data = 4bits (signed)
 172 // Channel volume = 12bits
 173 // Envelope volume = 14bits
 174 // Master volume = 2bits
 175
 176 // Recalculate left and right volume as volume changes.
 177 // To calculate the current sample, use (sample * volume) >> 16
 178
 179 // Square waves range from -8 (low) to 7 (high)
 180
 181 s8 square_pattern_duty[4][8] =
 182 {
 183   { 0xF8, 0xF8, 0xF8, 0xF8, 0x07, 0xF8, 0xF8, 0xF8 },
 184   { 0xF8, 0xF8, 0xF8, 0xF8, 0x07, 0x07, 0xF8, 0xF8 },
 185   { 0xF8, 0xF8, 0x07, 0x07, 0x07, 0x07, 0xF8, 0xF8 },
 186   { 0x07, 0x07, 0x07, 0x07, 0xF8, 0xF8, 0x07, 0x07 },
 187 };
 188
 189 s8 wave_samples[64];
 190
 191 u32 noise_table15[1024];
 192 u32 noise_table7[4];
 193
 194 u32 gbc_sound_master_volume_table[4] = { 1, 2, 4, 0 };
 195
 196 u32 gbc_sound_channel_volume_table[8] =
 197 {
 198   fixed_div(0, 7, 12),
 199   fixed_div(1, 7, 12),
 200   fixed_div(2, 7, 12),
 201   fixed_div(3, 7, 12),
 202   fixed_div(4, 7, 12),
 203   fixed_div(5, 7, 12),
 204   fixed_div(6, 7, 12),
 205   fixed_div(7, 7, 12)
 206 };
 207
 208 u32 gbc_sound_envelope_volume_table[16] =
 209 {
 210   fixed_div(0, 15, 14),
 211   fixed_div(1, 15, 14),
 212   fixed_div(2, 15, 14),
 213   fixed_div(3, 15, 14),
 214   fixed_div(4, 15, 14),
 215   fixed_div(5, 15, 14),
 216   fixed_div(6, 15, 14),
 217   fixed_div(7, 15, 14),
 218   fixed_div(8, 15, 14),
 219   fixed_div(9, 15, 14),
 220   fixed_div(10, 15, 14),
 221   fixed_div(11, 15, 14),
 222   fixed_div(12, 15, 14),
 223   fixed_div(13, 15, 14),
 224   fixed_div(14, 15, 14),
 225   fixed_div(15, 15, 14)
 226 };
 227
 228 u32 gbc_sound_buffer_index = 0;
 229 u32 gbc_sound_last_cpu_ticks = 0;
 230 u32 gbc_sound_partial_ticks = 0;
 231
 232 u32 gbc_sound_master_volume_left;
 233 u32 gbc_sound_master_volume_right;
 234 u32 gbc_sound_master_volume;
 235
 236 #define update_volume_channel_envelope(channel)                               \
 237   volume_##channel = gbc_sound_envelope_volume_table[envelope_volume] *       \
 238    gbc_sound_channel_volume_table[gbc_sound_master_volume_##channel] *        \
 239    gbc_sound_master_volume_table[gbc_sound_master_volume]                     \
 240
 241 #define update_volume_channel_noenvelope(channel)                             \
 242   volume_##channel = gs->wave_volume *                                        \
 243    gbc_sound_channel_volume_table[gbc_sound_master_volume_##channel] *        \
 244    gbc_sound_master_volume_table[gbc_sound_master_volume]                     \
 245
 246 #define update_volume(type)                                                   \
 247   update_volume_channel_##type(left);                                         \
 248   update_volume_channel_##type(right)                                         \
 249
 250 #define update_tone_sweep()                                                   \
 251   if(gs->sweep_status)                                                        \
 252   {                                                                           \
 253     u32 sweep_ticks = gs->sweep_ticks - 1;                                    \
 254                                                                               \
 255     if(sweep_ticks == 0)                                                      \
 256     {                                                                         \
 257       u32 rate = gs->rate;                                                    \
 258                                                                               \
 259       if(gs->sweep_direction)                                                 \
 260         rate = rate - (rate >> gs->sweep_shift);                              \
 261       else                                                                    \
 262         rate = rate + (rate >> gs->sweep_shift);                              \
 263                                                                               \
 264       if(rate > 2048)                                                         \
 265         rate = 2048;                                                          \
 266                                                                               \
 267       frequency_step = float_to_fp16_16(((131072.0f / (2048 - rate)) * 8.0f)  \
 268        / sound_frequency);                                                    \
 269                                                                               \
 270       gs->frequency_step = frequency_step;                                    \
 271       gs->rate = rate;                                                        \
 272                                                                               \
 273       sweep_ticks = gs->sweep_initial_ticks;                                  \
 274     }                                                                         \
 275     gs->sweep_ticks = sweep_ticks;                                            \
 276   }                                                                           \
 277
 278 #define update_tone_nosweep()                                                 \
 279
 280 #define update_tone_envelope()                                                \
 281   if(gs->envelope_status)                                                     \
 282   {                                                                           \
 283     u32 envelope_ticks = gs->envelope_ticks - 1;                              \
 284     envelope_volume = gs->envelope_volume;                                    \
 285                                                                               \
 286     if(envelope_ticks == 0)                                                   \
 287     {                                                                         \
 288       if(gs->envelope_direction)                                              \
 289       {                                                                       \
 290         if(envelope_volume != 15)                                             \
 291           envelope_volume = gs->envelope_volume + 1;                          \
 292       }                                                                       \
 293       else                                                                    \
 294       {                                                                       \
 295         if(envelope_volume != 0)                                              \
 296           envelope_volume = gs->envelope_volume - 1;                          \
 297       }                                                                       \
 298                                                                               \
 299       update_volume(envelope);                                                \
 300                                                                               \
 301       gs->envelope_volume = envelope_volume;                                  \
 302       gs->envelope_ticks = gs->envelope_initial_ticks;                        \
 303     }                                                                         \
 304     else                                                                      \
 305     {                                                                         \
 306       gs->envelope_ticks = envelope_ticks;                                    \
 307     }                                                                         \
 308   }                                                                           \
 309
 310 #define update_tone_noenvelope()                                              \
 311
 312 #define update_tone_counters(envelope_op, sweep_op)                           \
 313   tick_counter += gbc_sound_tick_step;                                        \
 314   if(tick_counter > 0xFFFF)                                                   \
 315   {                                                                           \
 316     if(gs->length_status)                                                     \
 317     {                                                                         \
 318       u32 length_ticks = gs->length_ticks - 1;                                \
 319       gs->length_ticks = length_ticks;                                        \
 320                                                                               \
 321       if(length_ticks == 0)                                                   \
 322       {                                                                       \
 323         gs->active_flag = 0;                                                  \
 324         break;                                                                \
 325       }                                                                       \
 326     }                                                                         \
 327                                                                               \
 328     update_tone_##envelope_op();                                              \
 329     update_tone_##sweep_op();                                                 \
 330                                                                               \
 331     tick_counter &= 0xFFFF;                                                   \
 332   }                                                                           \
 333
 334 #define gbc_sound_render_sample_right()                                       \
 335   sound_buffer[buffer_index + 1] += (current_sample * volume_right) >> 22     \
 336
 337 #define gbc_sound_render_sample_left()                                        \
 338   sound_buffer[buffer_index] += (current_sample * volume_left) >> 22          \
 339
 340 #define gbc_sound_render_sample_both()                                        \
 341   gbc_sound_render_sample_right();                                            \
 342   gbc_sound_render_sample_left()                                              \
 343
 344 #define gbc_sound_render_samples(type, sample_length, envelope_op, sweep_op)  \
 345   for(i = 0; i < buffer_ticks; i++)                                           \
 346   {                                                                           \
 347     current_sample =                                                          \
 348      sample_data[fp16_16_to_u32(sample_index) % sample_length];               \
 349     gbc_sound_render_sample_##type();                                         \
 350                                                                               \
 351     sample_index += frequency_step;                                           \
 352     buffer_index = (buffer_index + 2) % BUFFER_SIZE;                          \
 353                                                                               \
 354     update_tone_counters(envelope_op, sweep_op);                              \
 355   }                                                                           \
 356
 357 #define gbc_noise_wrap_full 32767
 358
 359 #define gbc_noise_wrap_half 126
 360
 361 #define get_noise_sample_full()                                               \
 362   current_sample =                                                            \
 363    ((s32)(noise_table15[fp16_16_to_u32(sample_index) >> 5] <<                 \
 364    (fp16_16_to_u32(sample_index) & 0x1F)) >> 31) & 0x0F                       \
 365
 366 #define get_noise_sample_half()                                               \
 367   current_sample =                                                            \
 368    ((s32)(noise_table7[fp16_16_to_u32(sample_index) >> 5] <<                  \
 369    (fp16_16_to_u32(sample_index) & 0x1F)) >> 31) & 0x0F                       \
 370
 371 #define gbc_sound_render_noise(type, noise_type, envelope_op, sweep_op)       \
 372   for(i = 0; i < buffer_ticks; i++)                                           \
 373   {                                                                           \
 374     get_noise_sample_##noise_type();                                          \
 375     gbc_sound_render_sample_##type();                                         \
 376                                                                               \
 377     sample_index += frequency_step;                                           \
 378                                                                               \
 379     if(sample_index >= u32_to_fp16_16(gbc_noise_wrap_##noise_type))           \
 380       sample_index -= u32_to_fp16_16(gbc_noise_wrap_##noise_type);            \
 381                                                                               \
 382     buffer_index = (buffer_index + 2) % BUFFER_SIZE;                          \
 383     update_tone_counters(envelope_op, sweep_op);                              \
 384   }                                                                           \
 385
 386 #define gbc_sound_render_channel(type, sample_length, envelope_op, sweep_op)  \
 387   buffer_index = gbc_sound_buffer_index;                                      \
 388   sample_index = gs->sample_index;                                            \
 389   frequency_step = gs->frequency_step;                                        \
 390   tick_counter = gs->tick_counter;                                            \
 391                                                                               \
 392   update_volume(envelope_op);                                                 \
 393                                                                               \
 394   switch(gs->status)                                                          \
 395   {                                                                           \
 396     case GBC_SOUND_INACTIVE:                                                  \
 397       break;                                                                  \
 398                                                                               \
 399     case GBC_SOUND_LEFT:                                                      \
 400       gbc_sound_render_##type(left, sample_length, envelope_op, sweep_op);    \
 401       break;                                                                  \
 402                                                                               \
 403     case GBC_SOUND_RIGHT:                                                     \
 404       gbc_sound_render_##type(right, sample_length, envelope_op, sweep_op);   \
 405       break;                                                                  \
 406                                                                               \
 407     case GBC_SOUND_LEFTRIGHT:                                                 \
 408       gbc_sound_render_##type(both, sample_length, envelope_op, sweep_op);    \
 409       break;                                                                  \
 410   }                                                                           \
 411                                                                               \
 412   gs->sample_index = sample_index;                                            \
 413   gs->tick_counter = tick_counter;                                            \
 414
 415 #define gbc_sound_load_wave_ram(bank)                                         \
 416   wave_bank = wave_samples + (bank * 32);                                     \
 417   for(i = 0, i2 = 0; i < 16; i++, i2 += 2)                                    \
 418   {                                                                           \
 419     current_sample = wave_ram[i];                                             \
 420     wave_bank[i2] = (((current_sample >> 4) & 0x0F) - 8);                     \
 421     wave_bank[i2 + 1] = ((current_sample & 0x0F) - 8);                        \
 422   }                                                                           \
 423
 424 void update_gbc_sound(u32 cpu_ticks)
 425 {
 426   fixed16_16 buffer_ticks = float_to_fp16_16((float)(cpu_ticks -
 427    gbc_sound_last_cpu_ticks) * sound_frequency / GBC_BASE_RATE);
 428   u32 i, i2;
 429   gbc_sound_struct *gs = gbc_sound_channel;
 430   fixed16_16 sample_index, frequency_step;
 431   fixed16_16 tick_counter;
 432   u32 buffer_index;
 433   s32 volume_left, volume_right;
 434   u32 envelope_volume;
 435   s32 current_sample;
 436   u32 sound_status = address16(io_registers, 0x84) & 0xFFF0;
 437   s8 *sample_data;
 438   s8 *wave_bank;
 439   u8 *wave_ram = ((u8 *)io_registers) + 0x90;
 440
 441   gbc_sound_partial_ticks += fp16_16_fractional_part(buffer_ticks);
 442   buffer_ticks = fp16_16_to_u32(buffer_ticks);
 443
 444   if(gbc_sound_partial_ticks > 0xFFFF)
 445   {
 446     buffer_ticks += 1;
 447     gbc_sound_partial_ticks &= 0xFFFF;
 448   }
 449
 450   SDL_LockMutex(sound_mutex);
 451   if(synchronize_flag)
 452   {
 453     if(((gbc_sound_buffer_index - sound_buffer_base) % BUFFER_SIZE) >=
 454      (audio_buffer_size * 2))
 455     {
 456       while(((gbc_sound_buffer_index - sound_buffer_base) % BUFFER_SIZE) >
 457        (audio_buffer_size * 3 / 2))
 458       {
 459         SDL_CondWait(sound_cv, sound_mutex);
 460       }
 461
 462 #ifdef PSP_BUILD
 463       if(current_frameskip_type == auto_frameskip)
 464       {
 465         sceDisplayWaitVblankStart();
 466         real_frame_count = 0;
 467         virtual_frame_count = 0;
 468       }
 469 #else
 470       if(current_frameskip_type == auto_frameskip)
 471       {
 472 /*
 473         u64 current_ticks;
 474         u64 next_ticks;
 475         get_ticks_us(&current_ticks);
 476
 477         next_ticks = ((current_ticks + 16666) / 16667) * 16667;
 478         delay_us(next_ticks - current_ticks);
 479
 480         get_ticks_us(&frame_count_initial_timestamp);
 481 */
 482         /* prevent frameskip, or it will cause more audio,
 483          * then more waiting here, then frame skip again, ... */
 484         num_skipped_frames = 100;
 485       }
 486 #endif
 487
 488     }
 489   }
 490   if(sound_on == 1)
 491   {
 492     gs = gbc_sound_channel + 0;
 493     if(gs->active_flag)
 494     {
 495       sound_status |= 0x01;
 496       sample_data = gs->sample_data;
 497       envelope_volume = gs->envelope_volume;
 498       gbc_sound_render_channel(samples, 8, envelope, sweep);
 499     }
 500
 501     gs = gbc_sound_channel + 1;
 502     if(gs->active_flag)
 503     {
 504       sound_status |= 0x02;
 505       sample_data = gs->sample_data;
 506       envelope_volume = gs->envelope_volume;
 507       gbc_sound_render_channel(samples, 8, envelope, nosweep);
 508     }
 509
 510     gs = gbc_sound_channel + 2;
 511     if(gbc_sound_wave_update)
 512     {
 513       if(gs->wave_bank == 1)
 514       {
 515         gbc_sound_load_wave_ram(1);
 516       }
 517       else
 518       {
 519         gbc_sound_load_wave_ram(0);
 520       }
 521
 522       gbc_sound_wave_update = 0;
 523     }
 524
 525     if((gs->active_flag) && (gs->master_enable))
 526     {
 527       sound_status |= 0x04;
 528       sample_data = wave_samples;
 529       if(gs->wave_type == 0)
 530       {
 531         if(gs->wave_bank == 1)
 532           sample_data += 32;
 533
 534         gbc_sound_render_channel(samples, 32, noenvelope, nosweep);
 535       }
 536       else
 537       {
 538         gbc_sound_render_channel(samples, 64, noenvelope, nosweep);
 539       }
 540     }
 541
 542     gs = gbc_sound_channel + 3;
 543     if(gs->active_flag)
 544     {
 545       sound_status |= 0x08;
 546       envelope_volume = gs->envelope_volume;
 547
 548       if(gs->noise_type == 1)
 549       {
 550         gbc_sound_render_channel(noise, half, envelope, nosweep);
 551       }
 552       else
 553       {
 554         gbc_sound_render_channel(noise, full, envelope, nosweep);
 555       }
 556     }
 557   }
 558
 559   address16(io_registers, 0x84) = sound_status;
 560
 561   gbc_sound_last_cpu_ticks = cpu_ticks;
 562   gbc_sound_buffer_index =
 563    (gbc_sound_buffer_index + (buffer_ticks * 2)) % BUFFER_SIZE;
 564
 565   SDL_UnlockMutex(sound_mutex);
 566
 567   SDL_CondSignal(sound_cv);
 568 }
 569
 570 #define sound_copy_normal()                                                   \
 571   current_sample = source[i]                                                  \
 572
 573 #define sound_copy(source_offset, length, render_type)                        \
 574   _length = (length) / 2;                                                     \
 575   source = (s16 *)(sound_buffer + source_offset);                             \
 576   for(i = 0; i < _length; i++)                                                \
 577   {                                                                           \
 578     sound_copy_##render_type();                                               \
 579     if(current_sample > 2047)                                                 \
 580       current_sample = 2047;                                                  \
 581     if(current_sample < -2048)                                                \
 582       current_sample = -2048;                                                 \
 583                                                                               \
 584     stream_base[i] = current_sample << 4;                                     \
 585     source[i] = 0;                                                            \
 586   }                                                                           \
 587
 588 #define sound_copy_null(source_offset, length)                                \
 589   _length = (length) / 2;                                                     \
 590   source = (s16 *)(sound_buffer + source_offset);                             \
 591   for(i = 0; i < _length; i++)                                                \
 592   {                                                                           \
 593     stream_base[i] = 0;                                                       \
 594     source[i] = 0;                                                            \
 595   }                                                                           \
 596
 597
 598 void sound_callback(void *userdata, Uint8 *stream, int length)
 599 {
 600   u32 sample_length = length / 2;
 601   u32 _length;
 602   u32 i;
 603   s16 *stream_base = (s16 *)stream;
 604   s16 *source;
 605   s32 current_sample;
 606
 607   SDL_LockMutex(sound_mutex);
 608
 609   while(((gbc_sound_buffer_index - sound_buffer_base) % BUFFER_SIZE) <
 610    length && !sound_exit_flag)
 611   {
 612     SDL_CondWait(sound_cv, sound_mutex);
 613   }
 614
 615   if(global_enable_audio)
 616   {
 617     if((sound_buffer_base + sample_length) >= BUFFER_SIZE)
 618     {
 619       u32 partial_length = (BUFFER_SIZE - sound_buffer_base) * 2;
 620       sound_copy(sound_buffer_base, partial_length, normal);
 621       source = (s16 *)sound_buffer;
 622       sound_copy(0, length - partial_length, normal);
 623       sound_buffer_base = (length - partial_length) / 2;
 624     }
 625     else
 626     {
 627       sound_copy(sound_buffer_base, length, normal);
 628       sound_buffer_base += sample_length;
 629     }
 630   }
 631   else
 632   {
 633     if((sound_buffer_base + sample_length) >= BUFFER_SIZE)
 634     {
 635       u32 partial_length = (BUFFER_SIZE - sound_buffer_base) * 2;
 636       sound_copy_null(sound_buffer_base, partial_length);
 637       source = (s16 *)sound_buffer;
 638       sound_copy(0, length - partial_length, normal);
 639       sound_buffer_base = (length - partial_length) / 2;
 640     }
 641     else
 642     {
 643       sound_copy_null(sound_buffer_base, length);
 644       sound_buffer_base += sample_length;
 645     }
 646   }
 647
 648   SDL_CondSignal(sound_cv);
 649
 650   SDL_UnlockMutex(sound_mutex);
 651 }
 652
 653 // Special thanks to blarrg for the LSFR frequency used in Meridian, as posted
 654 // on the forum at http://meridian.overclocked.org:
 655 // http://meridian.overclocked.org/cgi-bin/wwwthreads/showpost.pl?Board=merid
 656 // angeneraldiscussion&Number=2069&page=0&view=expanded&mode=threaded&sb=4
 657 // Hope you don't mind me borrowing it ^_-
 658
 659 void init_noise_table(u32 *table, u32 period, u32 bit_length)
 660 {
 661   u32 shift_register = 0xFF;
 662   u32 mask = ~(1 << bit_length);
 663   s32 table_pos, bit_pos;
 664   u32 current_entry;
 665   u32 table_period = (period + 31) / 32;
 666
 667   // Bits are stored in reverse order so they can be more easily moved to
 668   // bit 31, for sign extended shift down.
 669
 670   for(table_pos = 0; table_pos < table_period; table_pos++)
 671   {
 672     current_entry = 0;
 673     for(bit_pos = 31; bit_pos >= 0; bit_pos--)
 674     {
 675       current_entry |= (shift_register & 0x01) << bit_pos;
 676
 677       shift_register =
 678        ((1 & (shift_register ^ (shift_register >> 1))) << bit_length) |
 679        ((shift_register >> 1) & mask);
 680     }
 681
 682     table[table_pos] = current_entry;
 683   }
 684 }
 685
 686 void reset_sound()
 687 {
 688   direct_sound_struct *ds = direct_sound_channel;
 689   gbc_sound_struct *gs = gbc_sound_channel;
 690   u32 i;
 691
 692   SDL_LockMutex(sound_mutex);
 693
 694   sound_on = 0;
 695   sound_buffer_base = 0;
 696   sound_last_cpu_ticks = 0;
 697   memset(sound_buffer, 0, sizeof(sound_buffer));
 698
 699   for(i = 0; i < 2; i++, ds++)
 700   {
 701     ds->buffer_index = 0;
 702     ds->status = DIRECT_SOUND_INACTIVE;
 703     ds->fifo_top = 0;
 704     ds->fifo_base = 0;
 705     ds->fifo_fractional = 0;
 706     ds->last_cpu_ticks = 0;
 707     memset(ds->fifo, 0, 32);
 708   }
 709
 710   gbc_sound_buffer_index = 0;
 711   gbc_sound_last_cpu_ticks = 0;
 712   gbc_sound_partial_ticks = 0;
 713
 714   gbc_sound_master_volume_left = 0;
 715   gbc_sound_master_volume_right = 0;
 716   gbc_sound_master_volume = 0;
 717   memset(wave_samples, 0, 64);
 718
 719   for(i = 0; i < 4; i++, gs++)
 720   {
 721     gs->status = GBC_SOUND_INACTIVE;
 722     gs->sample_data = square_pattern_duty[2];
 723     gs->active_flag = 0;
 724   }
 725
 726   SDL_UnlockMutex(sound_mutex);
 727 }
 728
 729 void sound_exit()
 730 {
 731   gbc_sound_buffer_index =
 732    (sound_buffer_base + audio_buffer_size) % BUFFER_SIZE;
 733   SDL_PauseAudio(1);
 734   sound_exit_flag = 1;
 735   SDL_CondSignal(sound_cv);
 736   SDL_CloseAudio();
 737 }
 738
 739 void init_sound()
 740 {
 741   SDL_AudioSpec sound_settings;
 742
 743 #ifdef PSP_BUILD
 744   audio_buffer_size = (audio_buffer_size_number * 1024) + 3072;
 745 #else
 746   audio_buffer_size = 16 << audio_buffer_size_number;
 747 //  audio_buffer_size = 16384;
 748 #endif
 749
 750   SDL_AudioSpec desired_spec =
 751   {
 752     sound_frequency,
 753     AUDIO_S16,
 754     2,
 755     0,
 756     audio_buffer_size / 4,
 757     0,
 758     0,
 759     sound_callback,
 760     NULL
 761   };
 762
 763   sound_mutex = SDL_CreateMutex();
 764   sound_cv = SDL_CreateCond();
 765
 766   SDL_OpenAudio(&desired_spec, &sound_settings);
 767   sound_frequency = sound_settings.freq;
 768   audio_buffer_size = sound_settings.size;
 769   u32 i = audio_buffer_size / 16;
 770   for (audio_buffer_size_number = 0; i && (i & 1) == 0; i >>= 1)
 771     audio_buffer_size_number++;
 772 #ifndef PSP_BUILD
 773   printf("audio: freq %d, size %d\n", sound_frequency, audio_buffer_size);
 774 #endif
 775
 776   gbc_sound_tick_step =
 777    float_to_fp16_16(256.0f / sound_frequency);
 778
 779   init_noise_table(noise_table15, 32767, 14);
 780   init_noise_table(noise_table7, 127, 6);
 781
 782   reset_sound();
 783
 784   SDL_PauseAudio(0);
 785 }
 786
 787 #define sound_savestate_builder(type)                                       \
 788 void sound_##type##_savestate(file_tag_type savestate_file)                 \
 789 {                                                                           \
 790   file_##type##_variable(savestate_file, sound_on);                         \
 791   file_##type##_variable(savestate_file, sound_buffer_base);                \
 792   file_##type##_variable(savestate_file, sound_last_cpu_ticks);             \
 793   file_##type##_variable(savestate_file, gbc_sound_buffer_index);           \
 794   file_##type##_variable(savestate_file, gbc_sound_last_cpu_ticks);         \
 795   file_##type##_variable(savestate_file, gbc_sound_partial_ticks);          \
 796   file_##type##_variable(savestate_file, gbc_sound_master_volume_left);     \
 797   file_##type##_variable(savestate_file, gbc_sound_master_volume_right);    \
 798   file_##type##_variable(savestate_file, gbc_sound_master_volume);          \
 799   file_##type##_array(savestate_file, wave_samples);                        \
 800   file_##type##_array(savestate_file, direct_sound_channel);                \
 801   file_##type##_array(savestate_file, gbc_sound_channel);                   \
 802 }                                                                           \
 803
 804 sound_savestate_builder(read);
 805 sound_savestate_builder(write_mem);
 806